hippocampus 2 human 2 pattern separation Aged 1 Aged, 80 and over 1 Aging 1 CA3 Region, Hippocampal 1 Cardiorespiratory Fitness 1 Dentate Gyrus 1 Discrimination Learning 1 Female 1 Humans 1 MRI 1 Magnetic Resonance Imaging 1 Male 1 Middle Aged 1 Sex Factors 1 Task Performance and Analysis 1 adult 1 aerobic exercise 1 aged 1 aging 1 anatomy and histology 1 article 1 body volume 1 cardiorespiratory fitness 1 clinical trial 1 dentate gyrus 1 diagnostic imaging 1 discrimination learning 1